Dear John: I'm afraid that all of the data and my personal experience with heart patients is that prolonged exposure to high ambient temperatures (>99 F) is deleterious because of the associated increase in heart rate that places an extra burden on an already weakened heart. The warm environment may make the individual feel relaxed, while his heart is actually under the stress imposed by the elevated ambient temperature. The way that the heat is generated makes no difference. To summarize: there is no physiologic basis for these claims. Please consult with your physician about appropriate exercise.